Elastic diaphragm switch

ABSTRACT

An elastic diaphragm switch has a diaphragm assembly formed as an airtight interface between a substantially rigid substrate material and a diaphragm of highly flexible film to which is adhered a copper conductive pattern designed to withstand large deflections without fatigue. This is accomplished by an extended length conductor such as a spiral conductor path extending from the diaphragm supported contact to a stationary conductor. Thus the diaphragm switch may be formed of a single thin film and activated by very low-pressure levels.

United States Patent 2,811,599 10/1957 Statham 200/83.8 3,009,03211/1961 Friend et alm. 200/33.8 3,267,233 8/1966 Basile ZOO/83.83,331,040 7/1967 Woodhead 335/196 (X) 3,492,420 1/1970 Neville et a1.200/83 (X) 3,308,253 3/1967 Krakinowski 200/86 (X) FOREIGN PATENTS1,108,593 4/1968 Great Britain ZOO/83.8

Primary Examiner-Robert K. Schaefer Assistant ExaminerWi1liam J SmithAttorneysHani fin and Jancin and Robert W. Lahtinen [72] InventorsDonald F. Colglazier;

Myron E. Snesrud, both of Rochester, Minn. 21 1 Appl. No. 844,349 [22]Filed July 24, 1969 [45] Patented July 20, 1971 [73] Assigneelntemational Business Machines Corporation Armonk, N.Y.

[54] ELASTIC DIAPHRAGM SWITCH 9 Claims, 6 Drawing Figs.

[52] US. Cl 200/83 B, 200/83 N, 200/159 B 51] Int. Cl non 35 34 [50]Field ofSearch 200/83, 83.2, 83.8,159 B [56] References Cited UNITEDSTATES PATENTS 541,243 6/1895 Manger 200/159 B 3,240,885 3/1966Grunfelder... 200/5 R 3,515,828 6/1970 Boerner..... 200/83 R 2,798,1307/1957 Cox ZOO/83.2

ATENTED 'JUL20 197i SHEET 1 BF 2 MVf/l/WS. DONALD F. COLGLAZIER MYRON E.SNESRUD ATTORNEY ELASTIC DIAPHRAGM SWITCH BACKGROUND OF THE INVENTIONThis invention pertains to elastic diaphragm switches and moreparticularly to low-pressure fluid-actuated diaphragm switches.

Elastic diaphragm switches have commonly been made by adhering a layerof conductive material to a flexible substrate such as polyester filmwith an overlying coversheet of elastic material to further resistabrasion or permanent deformation. Multiple layers of deformablematerials and the impairment of the flexibility caused by the presenceof conductors increases the necessary operating pressures required andlimits the density of switches that may be placed in a given space.Further the fatigue of conductors induced by the flexing action limitedthe effective life of the individual switches.

This invention is directed to an elastic diaphragm switch utilizing athin film of highly flexible material formed as an airtight diaphragm.The diaphragm is deflected through such distances as 0.012 inch ratherthan the more typical 0.002 inch using the less flexible substratematerials such as previously utilized. To accommodate the increaseddeflections without fatigue, the copper conductive pattern extendingfrom the diaphragm carriedcontact to a stationary lead extends in ahelical'pattern to thereby approach a disposition perpendicular to theradial elongation of the diaphragm material and reduce the conductorflcxure per unit length to minimize the fatigue load to which theconductor is subjected. This simultaneously reduces the impairment ofdiaphragm flexibility caused by the adhered conductive material.

The diaphragm switch made in accordance with the present invention ishigh speed and economical. Using thin film polymer plastics, it has beenpossible to achieve response rates of 2,000 cycles per second using a0.005 inch gap. Further, with diaphragm assembly packaging densitiessuch as 16 per square inch, the structure can be readily fabricated atlow cost by automated paging or sheeting techniques. Also, the lowmasses involved in the structure cause the device to be virtuallyshockproof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged elevation viewof a document punching and verification device utilizing the elasticdiaphragm switch construction of this invention.

FIG. 2 is a section viewv taken along line 2--2 of FIG. 1.

FIG. 3 is an isometric view of the elastic diaphragm switch housingincluding the stationary contact circuit board which is an insert in themolded housing.

FIG. 4 is an isometric view of the stationary contact circuit boardshowing the major surface opposite that visible in FIG. 3.

FIG. 5 is an exploded view of the diaphragm and substrate assembly.

FIG. 6 is a fragmentary view of the elastic diaphragm material showingthe conductor pattern extending from the stationary diaphragm portion tothe movable contact.

FIG. 7 is an enlarged partial section of the diaphragm assemblyincluding the rigid substrate and flexible membrane.

DETAILED DESCRIPTION As illustrated in FIGS. I and 2 in an enlargedview, the elastic diaphragm switch assembly '10 is shown as a punchchecking or verifying device fora parallel punch where a card passing inparallel, row by row through the punch station along the card guidesurface 12 has rows of information punched therein. Two rows subsequentto the punching operation, the card is read to verify the informationentered. For each punch element 13 there is a corresponding readposition where a jet of air supplied through an orifice 14 is receivedby a passageway 15 whenever an unpunched card surface is not present toact as a valve. When the aligned orifice l4 delivers air to thepassageway 15, the elevated pressure applied at the terminal end of suchpassage causes the diaphragm 18 extending over a fluidtight circularinterface with the board 19 to be flexed outward therefrom bringing intoengagement the aligned contacts carried by the diaphragm 18 and thestationary circuit board 20.

The switch assembly 10 in the environment shown has normally closedcontacts as the passages 15 are subjected to airflow from therespectively aligned orifices 14. However, a punched card guided alongsurface 12 and passing through the read-verify station serves as a valveintermediate the orifices and aligned passageways. Accordingly, thelogic circuits as sociated with the device which are activated when acard is present would find the matrix to consist of normally openswitches and through the read timing circuit sense when a punched holehas permitted the associated diaphragm switch contacts to be closed.

The elastic diaphragm switch assembly 10 includes a molded housing 21which has a circuit board 20 held captive as an insert and a diaphragmassembly 23 which is received by the housing in abuttingrelation withshoulder 25 and is aligned by the surrounding wall surface 26.

The circuit board 20 is also shown in FIGS. 3 and 4. As seen in FIG. 4the epoxy circuit board has a series of terminals 28 individuallyconnected to contacts 29 which are plated through apertures 30 (shown inFIG. 2) in the circuit board to the enlarged contact surfaces 31 on theopposite surface that l are disposed within the housing as seen in FIG.3. The extended surface contacts 31 provide the stationary contacts ofthe elastic diaphragm switch assembly.

The diaphragm assembly 23, as shown exploded in FIG. 5, is fabricatedstarting with epoxy board 19 which is provided with a series ofapertures 35. Surrounding each of the apertures is a coating 36 ofnonstick material, such as a flurocarbon in a carrier which does notadhere to the diaphragm material, applied in a circular pattern radiallyoutward from each of the apertures. This nonstick material is selectedto prevent adhesion between the circuit board and the subsequentlyapplied overlying elastic film. The remaining surface 37 is coated withan adhesive. Over the surface which has thus been selectively coatedwith nonstick material and adhesive, a film 38 of highly flexiblematerial is applied which carries a conductive layer on the exposedsurface. The conductive material is thereafter etched to form anextended helical conductor path 40 from the stationary conductor portion41 disposed on the film portion adhered to the board and across theboundary 43 between adhered and nonadhered interfaces to the centralcontact 42 overlying the nonadhered interface. In the assembledcondition the common circuit 40 printed on the diaphragm 38 is connectedto a terminal on circuit board 20 by a conductor 39 which extends alongthe interface between gasket 48 and diaphragm assembly 23 and betweenmounting plate 45 and housing 21. As seen in FIG. 6 and FIG. 7, whenfluid pressure is applied through an aperture 35 to the otherwiseairtight circular interface between board 34 and diaphragm 38, thediaphragm flexes progressively from the adhesively bonded margin to thecenter which carries the contact 42 to correspondingly progressivelyflex the connecting conductor 40 thereby permitting substantialdeflection of the diaphragm carried contact without a localized fatiguebeing sustained by the conductor. Both the flexibility of the diaphragmmaterial and the minimum of constraint imposed by the conductor patternpermit actuation of the diaphragm by fluids subjected to very lowpressure.

Diaphragm assembly 23 is shown in enlarged form. In the specific deviceillustrated the major dimensions of the diaphragm assembly are 1 inch byone-half inch which yields a packaging density within the matrix of 16switches per square inch. The diaphragm 38 is a 0.001 inch polymer filmcarrying a circuit of 9% ounce copper which is gold plated. In theassembled condition there exists a spacing between diaphragm assembly 23and circuit board 20 of 0.005 inch. The switches are actuated by airdelivered from the aligned orifice 14 at a pressure of 1 pound persquare inch.

The elastic diaphragm is shown in an assembled section view in FIG. 2with passageways leading to the diaphragm chambers formed in mountingplate 45 and completed by a closure member 46. Continuity of thepassageway between mounting plate and board apertures and the separationof individual passages therebetween is maintained by the flexible gasket48 having a series of aligned openings 49. The individual elasticdiaphragm switch assemblies are secured to the mounting plate by straps50 which margin each transverse side. Conductors 52 leading from thecircuit board terminals are clamped between housing flange 53 and apressure block 54 to afford strain relief.

The nonadhered circular diaphragm portions of the switch assemblydeflect within the space defined by the circuit board 20, diaphragmassembly 23 and housing 21. To prevent the compression of air withinthis confined spaced from interfering with the proper operation of theswitches an extended volume is achieved by the central opening 55 in thecircuit board and housing 21 which communicate freely with the spacebounded by the housing 21 and closure plate 57 What we claim is: g

It A diaphragm switch assembly comprising:

a first contact carried by a substantially rigid insulating supportelement;

a diaphragm assembly including a flexible, electrically insulatingdiaphragm, supported in spaced relation to said support element;

a second contact carried by said diaphragm and aligned with said firstcontact;

a conductive lead adhered to the surface of said diaphragm whichconnects to said second contact and extends therefrom by an indirectroute along at least a portion of the surface of said diaphragm subjectto operational flexing; and

means for selectively varying the fluid pressure at one side of saiddiaphragm assembly second contact carrying portion to selectively engageand disengage said first and second contacts.

2. The diaphragm switch assembly of claim 1 wherein said diaphragmcomprises an elastic film and said conductive lead comprises a metalsurface portion plated on said elastic film.

3. The diaphragm switch assembly of claim 2 wherein said conductive leadis disposed in a substantially spiral configuration from said secondcontact along the said diaphragm surface subject to flexure.

4. The fluid-actuated switch of claim 3 wherein said lead extends from astationary location to the diaphragm carried con- 5. The diaphragmswitch assembly of claim 2 wherein said elastic diaphragm materialoverlies a substantially rigid member;

with an adhesive bond between said diaphragm and said member defining aclosed fluidtight nonadhering interface therebetween; and

passage means through said member communicating with said fluidtightinterface,

said lead extending in a generally spiral path from said contact acrossthe boundary between said adhesively bonded and nonadhesively bondedinterfaces.

6. The diaphragm switch assembly of claim 2 further comprising: 1

a substantially rigid nonconductive board member;

a nonstick material applied to discrete areas of one major surface ofsaid board,

said diaphragm material overlying said one major surface of said boardand selectively adhered to said board at least in area portionsmargining. said discrete area to form a fluidtight interface betweensaid board and diaphragm material; and

passage means formed in said board member communicating with each ofsaid fluidtight interfaces.

7. The diaphragm switch assembly of claim 6 wherein said electricalcontact is adhered to said dia h ragm material on the nonadhered surfacecentrally of said uidtight interface and said conductive lead extendssubstantially spirally from said electrical contact across the boundaryof said fluidtight interface.

8. A diaphragm switch assembly comprising:

a stationary first electrical contact;

a thin film elastic diaphragm;

a second electrical contact carried by said diaphragm in spacedconfronting relation with respect to said first contact;

an elongated conductor adhered to the surface of said diaphragm andextending from said second electrical contact by an indirect route alongthe surface of said diaphragm and means for varying the fluid pressureat one side of said diaphragm to cause deflection thereof to move saidsecond contact into and out of engagement with said first contact.

9. The diaphragm switch assembly of claim 8 wherein said second contactand said elongated conductor comprises a conductive pattern adhered tosaid diaphragm and said conductor extends from said second contact in agenerally spiral path.

1. A diaphragm switch assembly comprising: a first contact carried by asubstantially rigid insulating support element; a diaphragm assemblyincluding a flexible, electrically insulating diaphragm, supported inspaced relation to said support element; a second contact carried bysaid diaphragm and aligned with said first contact; a conductive leadadhered to the surface of said diaphragm which connects to said secondcontact and extends therefrom by an indirect route along at least aportion of the surface of said diaphragm subject to operational flexing;and means for selectively varying the fluid pressure at one side of saiddiaphragm assembly second contact carrying portion to selectively engageand disengage said first and second contacts.
 2. The diaphragm switchassembly of claim 1 wherein said diaphragm comprises an elastic film andsaid conductive lead comprises a metal surface portion plated on saidelastic film.
 3. The diaphragm switch assembly of claim 2 wherein saidconductive lead is disposed in a substantially spiral configuration fromsaid second contact along the said diaphragm surface subject to flexure.4. The fluid-actuated switch of claim 3 wherein said lead extends from astationary location to the diaphragm carried contact at an angle to thedirection of diaphragm material elongation approaching Perpendicular. 5.The diaphragm switch assembly of claim 2 wherein said elastic diaphragmmaterial overlies a substantially rigid member; with an adhesive bondbetween said diaphragm and said member defining a closed fluidtightnonadhering interface therebetween; and passage means through saidmember communicating with said fluidtight interface, said lead extendingin a generally spiral path from said contact across the boundary betweensaid adhesively bonded and nonadhesively bonded interfaces.
 6. Thediaphragm switch assembly of claim 2 further comprising: a substantiallyrigid nonconductive board member; a nonstick material applied todiscrete areas of one major surface of said board, said diaphragmmaterial overlying said one major surface of said board and selectivelyadhered to said board at least in area portions margining said discretearea to form a fluidtight interface between said board and diaphragmmaterial; and passage means formed in said board member communicatingwith each of said fluidtight interfaces.
 7. The diaphragm switchassembly of claim 6 wherein said electrical contact is adhered to saiddiaphragm material on the nonadhered surface centrally of saidfluidtight interface and said conductive lead extends substantiallyspirally from said electrical contact across the boundary of saidfluidtight interface.
 8. A diaphragm switch assembly comprising: astationary first electrical contact; a thin film elastic diaphragm; asecond electrical contact carried by said diaphragm in spacedconfronting relation with respect to said first contact; an elongatedconductor adhered to the surface of said diaphragm and extending fromsaid second electrical contact by an indirect route along the surface ofsaid diaphragm and means for varying the fluid pressure at one side ofsaid diaphragm to cause deflection thereof to move said second contactinto and out of engagement with said first contact.
 9. The diaphragmswitch assembly of claim 8 wherein said second contact and saidelongated conductor comprises a conductive pattern adhered to saiddiaphragm and said conductor extends from said second contact in agenerally spiral path.